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Eruption at Pu‘u ‘O‘o still going after 31 years

On Jan. 3, 2014, Kilauea’s Pu‘u ‘O‘o eruption surpasses 31 years of activity. The ongoing eruption has evolved tremendously during its complex history. While it is impossible to recount in detail every episode of this long-lived East Rift Zone eruption in a Volcano Watch article, we mark its anniversary with a recap of highlights through the years.

It came as no surprise to USGS Hawaiian Volcano Observatory scientists when a new fissure opened along Kilauea’s East Rift Zone on Jan. 3, 1983. This area had hosted a series of intrusions and short-lived eruptions from the early 1960s through the early 1980s. But after towering lava fountains began erupting from a single vent in June 1983, it was recognized that this eruption was different.

The lava fountains were episodic, with each eruption lasting about a day and occurring about every 3 weeks, and progressively built the pyroclastic cone now called Pu‘u ‘O‘o. In addition, the lava fountains spawned fast-moving ‘a‘a flows, some of which destroyed houses in the sparsely populated Royal Gardens subdivision.

In July 1986, the eruption shifted 3 kilometers (2 miles) to the east and changed style. Rather than episodic fountains, lava flows erupted nearly continuously, forming a low, broad lava shield that was later named Kupaianaha.

Pahoehoe flows erupted from Kupaianaha crept slowly downslope, building lava tubes as they advanced. These tubes insulated the molten lava, which enabled flows to travel farther and reach the more populous coastline. Over the following years, houses were buried on both sides of the widening flow field and the village of Kalapana was partially destroyed in 1990.

The Kupaianaha vent died in February 1992, when the eruption shifted to new vents on the southwest flank of the Pu‘u ‘O‘o cone. New lava tubes were constructed as the lava again advanced downslope—this time mostly within Hawai‘i Volcanoes National Park. A lava shield, pockmarked with collapse pits, slowly buried the southwest flank of Pu‘u ‘O‘o.

Eruption from Pu‘u ‘O‘o’s southwest flank vents predominated for the next 15 years, finally coming to an end in June 2007, when the Father’s Day fissure eruption occurred west of Pu‘u ‘O‘o. This change led to the establishment of a new vent between Pu‘u ‘O‘o and Kupaianaha that sent flows back to Kilauea’s southeast coast, where they destroyed several more homes in Royal Gardens and Kalapana Gardens subdivisions. Kilauea’s ongoing summit eruption also began during this period (in March 2008).

The next big change came in early March 2011, when the 4-day-long Kamoamoa fissure eruption west of Pu‘u ‘O‘o was followed by the cessation of eruptive activity along the East Rift Zone. But the eruption resumed in late March, and lava slowly filled the Pu‘u ‘O‘o crater over the following months. Then, in September 2011, the “Peace Day” vent opened high on the east flank of the Pu‘u ‘O‘o cone and sent lava flows back to Kilauea’s southeastern coast for the next two years.

In January 2013, the Peace Day flow, which was relatively weak compared to much of Pu‘u ‘O‘o’s past eruptive activity, was joined by a flow fed directly from a spatter cone at the northeast edge of the Pu‘u ‘O‘o crater floor. But this new flow — the Kahauale‘a flow — advanced toward the northeast rather than to the southeast. With the establishment of the Kahauale‘a flow, the Peace Day flow began to wane and, in November 2013, the Peace Day flow died.

The slow transition of activity from the Peace Day flow to the Kahauale‘a flow marks a dramatic change in the risk posed by the eruption. Unless there is a significant change at Pu‘u ‘O‘o, the Kahauale‘a flow poses no imminent threat to infrastructure, but will likely continue advancing toward the northeast, burning forest as it does. It could eventually reach communities far downslope, but fortunately, the East Rift Zone eruptive output remains weak. At its current pace, the Kahauale‘a flow would take more than a year to reach populated areas.

Over the past 31 years, just over 4 cubic kilometers (1 cubic mile) of lava have been erupted, covering 128 square kilometers (49 square miles) of land and destroying 214 structures. Only time will tell how the eruption evolves in the New Year. As the saying goes, “May you live in interesting times.”

Kilauea activity update A lava lake within Halema‘uma‘u produced nighttime glow that was visible via HVO’s Webcam during the past week. Summit tiltmeters recorded minor variations, but overall the tilt level was relatively steady. The lava lake level rose slowly and was about 45 meters (148 feet) below the rim of the Overlook crater on Thursday, Jan. 2.

On Kilauea’s East Rift Zone, the Kahauale‘a 2 flow continued to advance very slowly into the forest northeast of Pu‘u ‘O‘o. The active front of the flow was about 6.3 kilometers (3.9 miles) northeast of Pu‘u ‘O‘o when mapped on Dec. 26.

There were no earthquakes reported felt on the Island of Hawai‘i in the past week. Visit the HVO website (http://hvo.wr.usgs.gov) for Volcano Awareness Month events and current Kilauea, Mauna Loa, and Hualālai activity updates, recent volcano photos, recent earthquakes, and more; call 967-8862 for a Kilauea summary; email questions to askHVO@usgs.gov.

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